In the cosmetics and personal care industries, the use of silicone-based ingredients is well known. Generally, silicones have several very useful characteristics including high resistance to extreme temperatures, light stability, resistance to moisture and chemical exposure. Common applications for silicone products include their use as adhesives, surfactants and anti-foaming agents, while in cosmetics and personal care, silicones play a number of well defined roles that include smoothing, lubricating, moisturizing and conditioning.
One critical point is that silicone ingredients are used for their substantivity. Substantivity is the ability of a cosmetic ingredient to remain intact on the skin or hair even after the skin or hair has been rinsed with water. The advantage of good substantivity is that a conditioning agent can remain on the skin or hair for a considerable period of time to impart a benefit to the skin or hair. By considerable period of time, it is meant that the silicone ingredient is intended to remain intact on the skin or hair for at least several minutes or hours and is not easily removed, except with the aid of specific types of cleansers. In practice, cosmetic ingredients with good substantivity can remain on the skin or hair for hours or days and this is often intended. One drawback of ingredients with good substantivity is that they tend to build-up on the skin or hair with repeated applications over time. In time, this build-up itself becomes detrimental to the skin. In a novel way, the present invention utilizes silicone materials known for their good substantivity, while avoiding the problems of build up.
Some agents that exhibit good substantivity do so because of strong electrostatic attraction between the treated surface and the ingredient. Generally, silicones do not belong to this class. Silicones belong to a class of cosmetic ingredients that exhibit good substantivity because they are insoluble in water, and thus, once deposited on the skin or hair, are not easily washed away. Silicone products may be fluid, resinous or elastomeric, the exact form depending on the length of the polymer backbone and the degree of cross-linking. Because most silicones are not water soluble, significant research and development focuses on methods of incorporating silicone materials into aqueous delivery systems. In other words, the very property that gives silicones their excellent substantivity also complicates the formulation of silicones into stable, efficacious aqueous systems. For example, in cosmetics and personal care, where the product vehicle is frequently water based, it is often necessary to emulsify silicone oils and elastomers into an aqueous external phase using surfactants. This introduces additional complexity to the formula and full scale production, the costs of production are increased and additional limitations are placed on the formula because of the need to make an emulsion. For example, emulsifiers and surfactants are known to be skin irritants and so this needs to be taken into account. The present invention provides a stable, efficacious silicone elastomer formulation that is aqueous based, but may not require the addition of emulsifiers.
In the cosmetics industry, silicone elastomers may be considered as dry emollients. Emollients are agents that impart smoothness and lubricity to the skin or hair. In topical ointments, silicone elastomers impart sleekness and a silky and powdery feel to skin or hair. In make-up compositions they may also be used to modify shine or mattify the appearance of the skin and to impart long lasting waterproofing properties. Examples of known crosslinked silicone elastomers that are used for these purposes include the dimethicone-cyclomethicone and dimethicone-divinyldimethicone crosspolymers from Dow Corning; the organopolysiloxanes from Grant Industries known under the name Gransil; General Electric's dimethicone-vinyldimethicone crosspolymers and others. Although the elastomer is in powder form, once applied to the skin, as in prior art formulations, it still exhibits good substantivity and may not easily rinse off the skin. Compositions of the present invention are particularly concerned with solid silicone elastomers in powder form. However, the compositions herein described may be easily removed from the skin within seconds or minutes of their application without the aid of specific cleansers or removal agents or even a ready supply of water.
As mentioned, silicone elastomers may be incorporated into water based systems by emulsion techniques, however, it is also known to form suspensions of powdered silicone elastomers which may then be added to an aqueous base. Suspension of silicone elastomers will be preferred over emulsification when the silicone elastomer is non-hydrophilic, in nature and therefore, non-emulsifying. Suspending agents are generally used for this purpose. Silicone elastomer suspensions are also to be preferred over emulsion systems when it is desired to avoid the harsh, irritating side-effects of surfactants and emulsifiers or when it is desirable to reduce as mush as possible, the amount of these irritants. Furthermore, suspensions of the type contemplated are generally simpler to manufacture than emulsions.
One commercially available suspension of this type is Dow Corning© 9509 Silicone Elastomer Suspension, which is a 63% by weight, nonionic suspension in water, of powdered dimethicone/vinyl dimethicone crosspolymer (and) C12-14 pareth-12. According to a DC9509 Product Information Sheet (ref no. 27-1001-01; Aug. 17, 2001), the contents of which are herein, incorporated by reference, the silicone elastomer particles are spherical and have an average diameter of 3 μm. The range of particle sizes in DC 9509 is about 0.1 μm-100 μm. The recommended use of this material is by direct addition to an aqueous phase, such that the pure silicone elastomer is present at a level of 3-6 wt. % of the final formulation. Given that the suspension is 63 wt. % of silicone elastomer, the suspension should comprise approximately 5-10 wt. % of the final formulation in order to meet the manufacturer's recommendation of 3-6 wt. % silicone elastomer. In the Product Information Sheet, three examples are mentioned: a hydrogel containing 10% DC 9509, a hydrogel containing 8% DC 9509 and a water-in-silicone emulsion having 6.5% DC 9509 in the aqueous phase. Further examples of formulations with DC 9509 can be found at the websites of Dow Corning and National Starch. These include: Dow formulation 00035 Fresh Energizing Lotion with Reduced Shine, containing 10 wt. % DC 9509; Dow Formulation 00231 Matte Last Hydrogel, containing 5 wt. % DC 9509; Dow Formulation 00458 Shaving Jelly, containing 2 wt. % DC 9509; and National Starch 12002-63 Firming And Moisturizing Body Fluid, containing 6 wt. % DC 9509. In line with Dow's instructions, none of these formulations uses more than 10% DC 9509. The present invention includes stable and efficacious compositions with substantially more than 10% DC 9509.
U.S. Pat. No. 5,871,761 (the contents of which are herein, incorporated by reference) discloses a method of preparing water-based cosmetics comprising the steps of:
(a) preparing an aqueous dispersion (suspension) of globular (spherical) particles of a cured silicone rubber having a specified average particle diameter (0.1 to 100 μm, preferably 1 to 10 μm), by a particular method disclosed therein, and
(b) mixing a specified amount of the aqueous dispersion of silicone rubber particles with a base mixture that consists of the principal ingredients of a water-based toiletry composition.
The content of silicone rubber particles is specifically limited to 0.1-30 wt. % (preferably 1-10 wt. %) of the total amount of the non-volatile matters in the base mixture. The silicone content of the aqueous dispersions formed in step (a) are disclosed to be in the range of 1-70 wt. % of the aqueous dispersion. Therefore, step (a) encompasses Dow Corning 9509, discussed above, which is a 63% aqueous dispersion.
The upper limit of 30% in step (b) is explained at column 6, lines 29-32 of the '761 patent, which reads: “When the amount of the cured silicone rubber particles is too large, the inherent role to be played by the water-base[d] toiletry preparation may not be satisfactorily played or the stability of the water-base[d] toiletry preparation is decreased.” In other words, the '761 patent gives specific reasons for not formulating a water-based toiletry with silicone elastomers above about 30 wt. % of the total amount of the non-volatile matters in the base mixture. These reasons relate to a loss of efficacy and stability of the overall composition.
In practice, the prior art discloses uses of silicone elastomer powder at much lower than 30% of the weight of the non-volatile portion of the base mixture. In the four examples of the '761 patent, elastomer weight is less than 3%. In the four examples mentioned above (three from Dow Corning and one from National Starch), the silicone elastomer contents are between 1 and 8 wt. % of the total amount of the non-volatile matters in the base mixture. Thus, in practice, the prior art, including the '761 patent, has stayed well below the maximum amount of silicone elastomer powder recommended in the '761 patent. The present invention includes stable and efficacious compositions with DC 9509 at levels that are substantially more than 30% of the total amount of the non-volatile matters in the base mixture.
US publication 2004/0126349 discloses a non-emulsion, water-based composition comprising a suspended silicone elastomer. The preferred suspended elastomer is disclosed as DC 9509, which should be added to the composition at no more than 10% of the weight of the total composition, which is also the recommendation of Dow Corning, as discussed above. The preferred concentration of the silicone elastomer suspension is 0.1-5 wt. % and the most preferred is 0.5-2.5 wt. % of the total weight of the composition. In the only example in the publication, the weight of the silicone elastomer suspension is 2% of the total composition weight. The weight of the silicone elastomer itself, is less than 2 wt. % of the total amount of the non-volatile matters in the base mixture. Again, this is well below the upper limit disclosed in the '761 patent, discussed above and even further below the levels of the present invention.
US publication 2005/0036971 discloses high lipid-content, pearlescent cosmetic preparations comprising: C12-C40 fatty acids, C12-C40 fatty alcohols, amphophilic polymers and/or siloxane elastomers, sodium hydroxide solution and optionally C12-C40 polyethoxylated fatty acid esters. Preferred silicone elastomers are in spherical powder form, in suspension or emulsion and DC 9509 is disclosed as being particularly advantageous. The weight of pure silicone elastomer is disclosed as being from 0.5-10 wt. % of the total composition, although the examples demonstrate no more than 0.5 wt. % silicone elastomer in any composition. Again, this is well below the upper limit disclosed in the '761 patent, discussed above and even further below the levels of the present invention.
At paragraph [0074], the '971 publication teaches the following: “In addition, they [silicone elastomers] have stabilizing effects on formulations with a high content of oil and low water contents of at most 5% by weight.” This statement of the prior art certainly suggests that silicone elastomers fail to stabilize compositions that comprise more than 5% water. Bearing in mind that DC 9509 is about 37% water, any composition comprising at least about 14% of DC 9509 automatically contains more than 5% water. Thus, the '971 publication suggests that no benefit is obtained by formulating compositions with more than 14% DC 9509. The present invention advantageously comprises substantially more than 14% DC 9509 or any equivalents of 14% of DC 9509.
To the best of the applicant's knowledge, and as demonstrated by the foregoing discussion, efficacious and stable personal care compositions comprising an aqueous suspension of silicone elastomer particles, such that the weight of the silicone elastomer is greater than 30 wt. % of the total amount of the non-volatile matters in the base mixture, are unknown in the prior art. In fact, the examples disclosed in the prior art are all substantially below this level. The present invention goes against the teachings of the prior art to provide stable and efficacious compositions having silicone elastomers at greater than 30 wt. % of the total amount of the non-volatile matters in the base mixture . Furthermore, the present invention includes compositions comprising substantially more than 5% water.
Cosmetic or dermatologic exfoliation is the process of removing dead or degraded layers of skin cells from the top most surface of the skin in order to expose healthier cells below. Cosmetic exfoliation has a number of known and generally accepted benefits which include: providing a healthier, more attractive appearance to the skin; providing a “glow” to the skin; opening or unblocking the pores of the skin to facilitate the receiving of topically applied nutrients or other treatment benefits; encouraging increased blood flow in the skin; encouraging collagen formation in the skin leading to thicker, firmer, healthier skin. Among other things, exfoliation has been used to treat acne, irregular pigmentation, signs of ageing and scarring. For these and other reasons, exfoliation is widely recognized as one of the most important skin treatments for persons interested in improving the health and appearance of their skin. Techniques include mechanical abrasives, like scrubs, peels, and dermabrasion; chemical exfoliants in the form of peels, masques and other topical ointments; and laser treatment. In the first instance, the present invention is concerned with mechanical abrasion for the benefits that such impart to the skin. However, the incorporation of chemical exfoliants or use in conjunction with laser treatment is not outside the scope of this invention.
One draw back of some exfoliation techniques, particularly conventional peels and masques, is that there is a substantial drying time that the user must wait before the peel or masque can be removed. Frequently, leaving a thick layer of ointment on an extended portion of the skin, especially the face, is physically uncomfortable and socially inconvenient, as some people receiving these treatments prefer not to be seen during the course of a treatment. Compositions of the present invention are applied in the manner of creams, lotions and ointments, but there is a substantially reduced drying time compared to the prior art, and the exfoliation may be completed in much less time than other products, thus alleviating the physical and social discomfort associated with exfoliation treatment.
Another drawback of some exfoliation products is that they must be removed from the skin by rinsing with water or some other cleanser. Failure to do so leaves a residue on the skin which generally, compromises the appearance of the skin, is uncomfortable for the user and may cause irritation to the skin of the user. For this reason, and because some people prefer not to be seen receiving an exfoliation treatment, mechanical exfoliation with a cosmetic product is generally done at home or in a salon where a ready supply of water and privacy are available. In contrast, exfoliants of the present invention may be used to impart a benefit to the skin and then be removed from the skin with little or no water for rinsing. The treatment may be completed quickly and far more inconspicuously than conventional exfoliation treatments. Therefore, a user need not feel limited to the home or salon for treatment.
European Patent 0295886 discloses facial cleansers comprising a spherical silicone elastomer powder. According to the description, “. . . the organopolysiloxane elastomer used in the present invention provides the facial cleanser of the present invention with a smooth application sensation and does not irritate the skin.” Moreover, the specification says, “Prior facial cleansers which contain non-silicone powders have an unsatisfactory silicone-removal action because these powders lack any affinity for silicones. The organopolysiloxane elastomer powder has affinity for the silicone starting materials compounded in cosmetics and thus can remove silicones adhering on the skin.” Thus, in these compositions, the silicone elastomer is used primarily for its chemical affinity to other silicones, to lift those silicones from the skin. It has the simultaneous benefit, according to the authors, of going on smoothly and not causing irritation to the skin. It is clear from other parts of this disclosure that when the authors say “irritation” they mean mechanical irritation that is typical of the non-spherical, sharp, hard cleansing agents of the prior art. Thus, this reference suggests that the spherical nature of the silicone elastomer and its relative softness are useful for reducing mechanical abrasion. Put another way, EP 0295886 suggests the use of spherical silicone elastomer powders to reduce the action of exfoliation. Indeed, there is no mention in this reference of any exfoliation type activity or benefit. Therefore, the use of silicone elastomer powder in EP 0295886 is unlike the present invention, which uses silicone elastomer powder in a composition for mechanical exfoliation.
The '866 patent further discloses the use of silicone elastomer powder up to 30% of the composition, when the composition is a cream or emulsion (up to 50% when the composition is a solid or paste). Here again, the prior seems united on this point, placing an upper limit on the content of the silicone elastomer powder at around 30% of the non-solid composition. And, like the previous references, the examples in the '866 reference disclose amounts of silicone elastomer powder well below 30%, in this case, no more than 5% of silicone elastomer powder is present in any actual composition.
Furthermore, the '866 patent is an example of the fact that the use of soft, spherical particles in a composition may be expected to reduce the mechanical exfoliation action of the composition. Indeed, silicone elastomers and other silicone products are noted for the emolliency, lubricity, sleekness and powdery fell that they impart to compositions. All of these things are contrary to the type of mechanical abrasion required in exfoliating products. Nevertheless the present invention uses spherical silicone elastomer powder in a novel way to create a new type of exfoliating product.
A final observation of the prior art should be made, here. Based on the actual examples disclosed in the prior art, the totality of the prior art suggests that the instability and loss of efficacy associated with silicone elastomer particles, as discussed above, begin to appear somewhere below 30%, especially if more than 5% water is present in the composition. Therefore, the 30% upper limit from U.S. Pat. No. 5,871,761 is more accurately understood as a point of no return, as it were, rather than merely the onset of stability and efficacy problems.